Introduction
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AFS 224 User Manual
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AFS 224
Congratulations on your purchase of the dbx Professional Products AFS 224. The AFS 224
Advanced Feedback Suppression processor was designed to provide state-of-the-art feedback
elimination processing, while maintaining a simple and intuitive control interface. From the
powerful DSP module to the no-nonsense user interface, the AFS 224 provides all the process-
ing and control necessary for both installation and live use. The AFS 224 is an absolute must
for any live sound application.
Ten and twelve filter feedback elimination processors have become the de facto standard, but
the engineering staff at dbx have never been content residing in the neighborhood of the sta-
tus quo. So, to raise the bar once again, they went out and developed a dedicated feedback
suppression processor that offers up to 24 filters per channel with widths as narrow as 1/80 of
an octave. To achieve these staggering numbers dbx utilized their patent-pending AFS tech-
nology that had previously only been available in the upper echelon line of products and made
it available in this stand-alone processor. In addition to the plethora of feedback suppression
filters available, the AFS 224 also offers selectable modes, live filter lift, and types of filtration,
which are all readily available via the intuitive user interface front panel. This manual will be
your guide to understanding the full functionality of the powerful AFS 224 series.
The dbx AFS 224 provide the user with the following features:
• dbx’s patent-pending Advanced Feedback Suppression(AFS™)
technology
• 24 Programmable Filters per Channel
• Stereo or Dual Independent Channel Processing
• Live and Fixed Filter Modes
• Selectable Filter Lift Times
• Application-specific filter types include:Speech; Music Low,Med and High
• Input Channel Metering
• 24 Segment Filter Metering per Channel
• XLR and TRS Electronically Balanced Input and Outputs
The AFS 224 Advantage
Key features that make the AFS 224 are its Fixed and Live modes of operation, as well as the
units Filter Lift capabilities. The Live Mode of operation continuously updates filter placement
which provides flexibility during a performance. The Filter Lift feature automatically removes
filter assignments that are no longer necessary, which in turn, maximizes sonic integrity.
The AFS 224 allows the user to optimize the elimination of feedback. In the past, graphic equal-
izers were used to eliminate feedback from a system. This was an acceptable method for elim-
inating feedback, but when this method was precision tested, the result clearly showed that a
single 1/3 octave EQ slider was removing approximately half of the signal power. With the AFS,
the unit removes the feedback automatically and the proprietary, precision AFS filters remove
only a fraction of the frequency spectrum. The diagram on the following page shows AFS as
opposed to competitive feedback eliminators and conventional graphic EQs: